Plate-based Assay Research Articles

Oral Neutrophils Characterized: Chemotactic, Phagocytic, and Neutrophil Extracellular Trap (NET) Formation Properties.

Maintenance of oral health is in part managed by the immune-surveillance and antimicrobial functions of polymorphonuclear leukocytes (PMNs), which migrate from the circulatory system through the oral mucosal tissues as oral PMNs (oPMNs). In any microorganism-rich ecosystem, such as the oral cavity, PMNs migrate toward various exogenous chemoattractants, phagocytose bacteria, and produce neutrophil extracellular traps (NETs) to immobilize and eliminate pathogens. PMNs obtained from the circulation through venipuncture (hereafter called cPMNs) have been widely studied using various functional assays. We aimed to study the potential of oPMNs in maintaining oral health and therefore compared their chemotactic and antimicrobial functions with cPMNs. To establish chemotactic, phagocytic, and NET forming capacities, oPMNs and cPMNs were isolated from healthy subjects without obvious oral inflammation. Directional chemotaxis toward the chemoattractant fMLP was analyzed using an Insall chamber and video microscopy. fMLP expression was assessed by flow cytometry. Phagocytosis was analyzed by flow cytometry, following PMN incubation with heat-inactivated FITC-labeled micro-organisms. Furthermore, agar plate-based killing assays were performed with Escherichia coli (Ec). NET formation by oPMNs and cPMNs was quantified fluorimetrically using SYTOX™ Green, following stimulation with either PMA or RPMI medium (unstimulated control). In contrast to cPMNs, the chemotactic responses of oPMNs to fMLP did not differ from controls (mean velocity ± SEM of cPMNs: 0.79 ± 0.24; of oPMNs; 0.10 ± 0.07 micrometer/min). The impaired directional movement toward fMLP by oPMNs was explained by significantly lower fMLP receptor expression. Increased adhesion and internalization of various micro-organisms by oPMNs was observed. oPMNs formed 13 times more NETs than stimulated cPMNs, in both unstimulated and stimulated conditions. Compared to cPMNs, oPMNs showed a limited ability for intracellular killing of Ec. In conclusion, oPMNs showed exhausted capacity for efficient chemotaxis toward fMLP which may be the result of migration through the oral tissues into the oral cavity, being a highly “hostile” ecosystem. Overall, oPMNs' behavior is consistent with hyperactivity and frustrated killing. Nevertheless, oPMNs most likely contribute to maintaining a balanced oral ecosystem, as their ability to internalize microbes in conjunction with their abundant NET production remains after entering the oral cavity.

Physicochemical and microbiological assessment of spring water in central Himalayan region

In the present study, water quality of 16 springs, located along National Highway-58 from Rishikesh to Badrinath in India, was assessed by determining various physicochemical and microbiological parameters in three different seasons, i.e., pre-monsoon, monsoon, and post-monsoon. For majority of the springs, the pH was slightly alkaline with temperature ranging between 10 and 27°C. All other parameters such as total hardness (TH), total alkalinity (TA), chloride, phosphate, nitrate, total dissolved solids (TDS), electrical conductivity (EC), dissolved oxygen (DO), and biochemical oxygen demand (BOD) were found to lie within the acceptable limit prescribed by various standard national and international agencies. The principal component analysis reveals that water quality of springs mainly depends on mineral contents of water, as there is a loading of TH, TA, EC, TDS, and other mineral components during one or other season of a year. The positive correlation coefficients determined among mineral components of spring water further substantiate this fact. No loading of DO, BOD, nitrate, and phosphate indicates an absence of anthropogenic pollution in the studied area. No trace metals were detected in any of the springs. Most probable number (MPN) index for coliforms was found to be above the acceptable limit for all the springs in one or more seasons of a year, except the one in Pandukeshwar. Plate-based assay revealed the presence of pathogens like Salmonella, Shigella, Vibrio, and Pseudomonas in some spring water. The findings of the present work reveal that due to high MPN index and presence of other pathogenic bacteria, water from most of the springs cannot be considered completely safe for direct human consumption in its raw form.

Nanoliter Quantitative High-Throughput Screening with Large-Scale Tunable Gradients Based on a Microfluidic Droplet Robot under Unilateral Dispersion Mode.

Performing quantitative high throughput screening (qHTS) is in urgent need in current chemical, biological, and medical research. In this work, we developed an automated microfluidic dilution and large-scale screening system in the nanoliter range, by combining the droplet-based microfluidic robot technique with a novel unilateral Taylor-Aris dispersion-based dilution approach. The unilateral dispersion approach utilizes multiphase microfluidic design to generate a concentration gradient with fast gradient generation time, low sample/reagent consumption, and high operation efficiency over the widely used bilateral Taylor-Aris dispersion approach adopted in previous dilution systems. The present system is capable of automatically generating a large and tunable range of concentration gradients covering ca. 6 orders of magnitude in droplet arrays and achieving qHTS of a large number of different samples. We applied the microfluidic droplet system in miniaturized enzyme kinetic assay in 8-nL droplets and high-throughput quantitative screening of enzyme inhibitors with a library of 102 compounds. Only 9.8 μL of enzyme solution was consumed in 2448 droplet assays containing 102 compounds and 24 concentrations, representing an approximate 1600-fold reduction compared with multiwell plate-based assays. In the screening, dose-response curves of each tested compound were established and 4 hits (CP-471474, ilomastat, batimastat, and marimastat) were screened to have inhibitory activity to matrix metallopeptidase-9 (MMP-9), which demonstrated that the present system has the potential to provide a miniaturized qHTS platform for drug discovery.

An alternative biocontrol agent of soil-borne phytopathogens: A new antifungal compound produced by a plant growth promoting bacterium isolated from North Algeria

Bacteria isolated from different environments can be exploited for biocontrol purposes by the identification of the molecules involved in the antifungal activity. The present study was aimed at investigating antifungal protein compounds purified from a previously identified plant growth promoting bacterium, Pseudomonas protegens N isolated from agricultural land in northern Algeria. Therefore, a novel protein was purified by chromatographic and ultrafiltration steps and its antifungal activity together with growth-inhibition mechanism was evaluated against different fungi by plate-based assays. In addition, stereomicroscopy and transmission electron microscopy (TEM) was performed to explore the inhibition activity of the compound on spore germination processes. The protein, showing a molecular mass of about 100 kDa under native conditions, was revealed to be in the surface-membrane fraction and displayed an efficient activity against a variety of phytopathogenic fungi, being Alternaria the best target towards which it exhibited a marked fungicidal action and inhibition of spore germination. Moreover, the compound was able to significantly decrease fungal infection on tomato fruits producing also morphological aberrations on conidia. The obtained results suggested that the isolated compound could represent a promising agent for eco-friendly management of plant pathogens in agriculture.

Assessing Yeast Cell Survival Following Hydrogen Peroxide Exposure.

In the presence of oxidative stress, cellular defense systems that can detoxify reactive oxygen species are activated through multiple signaling cascades and transcriptional reprogramming. The budding yeast Saccharomyces cerevisiae has served as an excellent model for genetically-identifying factors important for the response to oxidative stress. Here, we describe two assays for testing yeast gene deletion strains or strains overexpressing a gene of interest for viability following oxidative stress induced by hydrogen peroxide treatment. These include a plate-based spot assay for visualizing cell growth and a quantitative colony counting assay. As stress response assays can be highly variable depending on cell growth conditions, these protocols have been optimized for obtaining highly-reproducible results between experiments. We demonstrate the use of these protocols for genetic tests of a putative chromatin regulator implicated in regulating the transcriptional response to oxidative stress.

Methods for Detecting N-Acyl Homoserine Lactone Production in Acinetobacter baumannii.

Acinetobacter baumannii cell-cell signaling is mediated by production and release of N-acyl homoserine lactones (AHLs), primarily N-(3-hydroxydodecanoyl)-L-homoserine lactone (3-hydroxy-C12-HSL). The secretion of this signal can be readily assessed via simple plate-based or thin-layer chromatography-based assays utilizing an Agrobacterium tumefaciens traG-lacZ containing biosensor. In this chapter, we describe methods to assay for secreted N-acyl homoserine lactone production in Acinetobacter baumannii.

I Plate-based Assay for Studying How Fungal Volatile Compounds (VCs) Affect Plant Growth and Development and the Identification of VCs via SPME-GC-MS.

Biogenic volatile compounds (VCs) mediate various types of crucial intra- and inter-species interactions in plants, animals, and microorganisms owing to their ability to travel through air, liquid, and porous soils. To study how VCs produced by Verticillium dahliae, a soilborne fungal pathogen, affect plant growth and development, we slightly modified a method previously used to study the effect of bacterial VCs on plant growth. The method involves culturing microbial cells and plants in I plate to allow only VC-mediated interaction. The modified protocol is simple to set up and produces reproducible results, facilitating studies on this poorly explored form of plant-fungal interactions. We also optimized conditions for extracting and identifying fungal VCs using solid phase microextraction (SPME) coupled to gas chromatography-mass spectrometry (GC-MS).

Multifunctional α-amylase Amy19 possesses agarase, carrageenase, and cellulase activities

The open reading frame of an α-amylase coding gene, amy19, was obtained from a fosmid genomic library of hot spring bacterium Bacillus BI-19 by a plate-based assay of carrageenase activity. After heterologous expression of the gene, the recombinant Amy19 was found to possess α-amylase, agarase, carrageenase, and cellulase activities, and could degrade soluble starch, agarose, carrageen, and sodium cellulose into oligosaccharides with low degrees of polymerization. To explore the multifunctional mechanism of Amy19, three continuous glycosyl hydrolase 70 (GH70) motifs in the Amy19 encoding sequence were deleted one by one, then in pairs, then all at once. The GH70 motifs may play an important role in the multifunctionality of Amy19, but the multifunctionality was not determined by the GH70 motifs alone. To our knowledge, this is the first report of an α-amylase from a hot spring bacterium with additional agarase, carrageenase, and cellulase activities.

Xylanolytic Psychotrophs From Andosolic Sedge Fens and Moss Heaths in Iceland

Nine xylanolytic bacterial strains were isolated from fen and heath soils in northern Iceland. They were found by 16S rRNA gene sequencing to belong to the genera Paenibacillus, Bacillus, Pseudomonas, and Stenotrophomonas. Using a simple, plate-based semiquantitative assay with azo-crosslinked xylan as the substrate, it was determined that although isolated from cold environments, most of the strains displayed greater xylanolytic activity under mesophilic conditions, with only the paenibacilli displaying markedly cold-active xylanolytic activity. Indeed, for one isolate, Paenibacillus castaneae OV2122, xylanolytic activity was only detected at 15°C and below under the conditions tested. Of the nine strains, Paenibacillus amylolyticus OV2121 displayed the greatest activity at 5°C. Glycohydrolase family-specific PCR indicated that the paenibacilli produced multiple xylanases of families 10 and 11, whereas a family 8 xylanase was detected in Pseudomonas kilonensis AL1515, and a family 11 xylanase in Stenotrophomonas rhizophila AL1610.

Phototaxis in a wild isolate of the cyanobacterium Synechococcus elongatus

Many cyanobacteria, which use light as an energy source via photosynthesis, have evolved the ability to guide their movement toward or away from a light source. This process, termed "phototaxis," enables organisms to localize in optimal light environments for improved growth and fitness. Mechanisms of phototaxis have been studied in the coccoid cyanobacterium Synechocystis sp. strain PCC 6803, but the rod-shaped Synechococcus elongatus PCC 7942, studied for circadian rhythms and metabolic engineering, has no phototactic motility. In this study we report a recent environmental isolate of S. elongatus, the strain UTEX 3055, whose genome is 98.5% identical to that of PCC 7942 but which is motile and phototactic. A six-gene operon encoding chemotaxis-like proteins was confirmed to be involved in phototaxis. Environmental light signals are perceived by a cyanobacteriochrome, PixJSe (Synpcc7942_0858), which carries five GAF domains that are responsive to blue/green light and resemble those of PixJ from Synechocystis Plate-based phototaxis assays indicate that UTEX 3055 uses PixJSe to sense blue and green light. Mutation of conserved functional cysteine residues in different GAF domains indicates that PixJSe controls both positive and negative phototaxis, in contrast to the multiple proteins that are employed for implementing bidirectional phototaxis in Synechocystis.

N-Naphthoyl-substituted indole thio-barbituric acid analogs inhibit the helicase activity of the hepatitis C virus NS3

The hepatitis C virus (HCV) represents a substantial threat to human health worldwide. The virus expresses a dual-function protein, NS3 having both protease and RNA helicase activities that are essential for productive viral replication and sustained infections. While viral protease and polymerase inhibitors have shown great successes in treating chronic HCV infections, drugs that specifically target the helicase activity have not advanced. A robust and quantitative 96-well plate-based fluorescent DNA unwinding assay was used to screen a class of indole thio-barbituric acid (ITBA) analogs using the full-length, recombinant HCV NS3, and identified three naphthoyl-containing analogs that efficiently inhibited NS3 helicase activity in a dose-dependent manner, with observed IC50 values of 21–24 µM. Standard gel electrophoresis helicase assays using radiolabeled duplex DNA and RNA NS3 substrates confirmed the inhibition of NS3 unwinding activity. Subsequent anisotropy measurements demonstrated that the candidate compounds did not disrupt NS3 binding to nucleic acids. Additionally, the rate of ATP hydrolysis and the protease activity were also not affected by the inhibitors. Thus, these results indicate that the three ITBA analogs containing N-naphthoyl moieties are the foundation of a potential series of small molecules capable of inhibiting NS3 activity via a novel interaction with the helicase domain that prevents the productive unwinding of nucleic acid substrates, and may represent the basis for a new class of therapeutic agents with the potential to aid in the treatment and eradication of hepatitis C virus.

DNA-linked inhibitor antibody assay (DIANA) as a new method for screening influenza neuraminidase inhibitors

Influenza neuraminidase is responsible for the escape of new viral particles from the infected cell surface. Several neuraminidase inhibitors are used clinically to treat patients or stockpiled for emergencies. However, the increasing development of viral resistance against approved inhibitors has underscored the need for the development of new antivirals effective against resistant influenza strains. A facile, sensitive, and inexpensive screening method would help achieve this goal. Recently, we described a multiwell plate-based DNA-linked inhibitor antibody assay (DIANA). This highly sensitive method can quantify femtomolar concentrations of enzymes. DIANA also has been applied to high-throughput enzyme inhibitor screening, allowing the evaluation of inhibition constants from a single inhibitor concentration. Here, we report the design, synthesis, and structural characterization of a tamiphosphor derivative linked to a reporter DNA oligonucleotide for the development of a DIANA-type assay to screen potential influenza neuraminidase inhibitors. The neuraminidase is first captured by an immobilized antibody, and the test compound competes for binding to the enzyme with the oligo-linked detection probe, which is then quantified by qPCR. We validated this novel assay by comparing it with the standard fluorometric assay and demonstrated its usefulness for sensitive neuraminidase detection as well as high-throughput screening of potential new neuraminidase inhibitors.

Mixing and delivery of multiple controlled oxygen environments to a single multiwell culture plate.

Precise oxygen control is critical to evaluating cell growth, molecular content, and stress response in cultured cells. We have designed, fabricated, and characterized a 96-well plate-based device that is capable of delivering eight static or dynamically changing oxygen environments to different rows on a single plate. The device incorporates a gas-mixing tree that combines two input gases to generate the eight gas mixtures that supply each row of the plate with a different gas atmosphere via a removable manifold. Using air and nitrogen as feed gases, a single 96-well plate can culture cells in applied gas atmospheres with Po2 levels ranging from 1 to 135 mmHg. Human cancer cell lines MCF-7, PANC-1, and Caco-2 were grown on a single plate under this range of oxygen levels. Only cells grown in wells exposed to Po2 ≤37 mmHg express the endogenous hypoxia markers hypoxia-inducible factor-1α and carbonic anhydrase IX. This design is amenable to multiwell plate-based molecular assays or drug dose-response studies in static or cycling hypoxia conditions.

A Caenorhabditis elegans assay of seizure-like activity optimised for identifying antiepileptic drugs and their mechanisms of action

BackgroundEpilepsy affects around 1% of people, but existing antiepileptic drugs (AEDs) only offer symptomatic relief and are ineffective in approximately 30% of patients. Hence, new AEDs are sorely needed. However, a major bottleneck is the low-throughput nature of early-stage AED screens in conventional rodent models. This process could potentially be expedited by using simpler invertebrate systems, such as the nematode Caenorhabditis elegans. New methodHead-bobbing convulsions were previously reported to be inducible by pentylenetetrazol (PTZ) in C. elegans with loss-of-function mutations in unc-49, which encodes a GABAA receptor. Given that epilepsy-linked mutations in human GABAA receptors are well documented, this could represent a clinically-relevant system for early-stage AED screens. However, the original agar plate-based assay is unsuited to large-scale screening and has not been validated for identifying AEDs. Therefore, we established an alternative streamlined, higher-throughput approach whereby mutants were treated with PTZ and AEDs via liquid-based incubation. ResultsConvulsions induced within minutes of PTZ exposure in unc-49 mutants were strongly inhibited by the established AED ethosuximide. This protective activity was independent of ethosuximide’s suggested target, the T-type calcium channel, as a null mutation in the worm cca-1 ortholog did not affect ethosuximide’s anticonvulsant action. Comparison with existing methodOur streamlined assay is AED-validated, feasible for higher throughput compound screens, and can facilitate insights into AED mechanisms of action. ConclusionsBased on an epilepsy-associated genetic background, this C. elegans unc-49 model of seizure-like activity presents an ethical, higher throughput alternative to conventional rodent seizure models for initial AED screens.

Biomarker analysis of fucosylated kininogen through depletion of lectin reactive heterophilic antibodies in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) accounts for >700,000 deaths worldwide, largely related to poor rates of diagnosis. Our previous work identified glycoproteins with increased levels of fucosylation in HCC. Plate-based assays to measure this change were compromised by increased levels of heterophilic antibodies with glycan lacking terminal galactose residues, which allowed for increased binding to the lectins used in these assays. To address this issue, we developed a multi-step protein A/G incubation and filtration method to remove the contaminating signal. However, this method was time consuming and expensive so alternative methods were desired. Herein, we describe a simple method relying on PEG precipitation that allows for the removal of IgG and IgM but retention of glycoproteins of interest. This method was tested on three sample sets, two internal and one external. PEG depletion of heterophilic IgG and IgM reduced in the coefficient of variation as observed with the protein A/G filtration method from 26.82% to 7.50% and allowed for the measurement of fucosylated protein. This method allowed for the measurement of fucosylated kininogen, which could serve as a biomarker of HCC. In conclusion, a new and simple method for the depletion of heterophilic IgG and IgM was developed and allowed for the analysis of fucosylated kininogen in patients with liver disease.

Automation vs. Experience: Measuring Alzheimer's Beta-Amyloid 1-42 Peptide in the CSF.

Cerebrospinal fluid (CSF) biomarkers can enhance the early and accurate etiologic detection of Alzheimer’s disease (AD) even when symptoms are very mild, but are not yet widely available for clinical testing. There are a number of reasons for this, including the need for an experienced operator, the use of instruments mostly reserved for research, and low cost-effectiveness when patient samples do not completely fill each assay plate. Newer technology can overcome some of these issues through automated assays of a single patient sample on existing clinical laboratory platforms, but it is not known how these newer automated assays compare with previous research-based measurements. This is a critical issue in the clinical translation of CSF AD biomarkers because most cohort and clinicopathologic studies have been analyzed on older assays. To determine the correlation of CSF beta-amyloid 1–42 (Aβ42) measures derived from the automated chemiluminescent enzyme immunoassay (CLEIA, on Lumipulse® G1200), a bead-based Luminex immunoassay, and a plate-based enzyme-linked immunoassay enzyme-linked immunosorbent assay (ELISA), we analyzed 30 CSF samples weekly on each platforms over 3 weeks. We found that, while CSF Aβ42 levels were numerically closer between CLEIA and ELISA measurements, levels differed between all three assays. CLEIA-based measures correlated linearly with the two other assays in the low and intermediate Aβ42 concentrations, while there was a linear correlation between Luminex assay and ELISA throughout all concentrations. For repeatability, the average intra-assay coefficient of variation (CV) was 2.0%. For intermediate precision, the inter-assay CV was lower in CLEIA (7.1%) than Luminex (10.7%, p = 0.009) and ELISA (10.8%, p = 0.009), primarily due to improved intermediate precision in the higher CSF Aβ42 concentrations. We conclude that the automated CLEIA generated reproducible CSF Aβ42 measures with improved intermediate precision over experienced operators using Luminex assays and ELISA, and are highly correlated with the manual Aβ42 measures.

Azithromycin Resistance in Clinical Isolates of Salmonella enterica Serovars Typhi and Paratyphi in Bangladesh.

Salmonella enterica serovars Typhi and Paratyphi, the causative agents of typhoid and paratyphoid, are major threats in developing countries. The present study aimed to investigate the resistance pattern of 40 clinically isolated Salmonella enterica serovars Typhi (n = 33) and Paratyphi (n = 7) to commonly used antibiotics, particularly azithromycin. The disc diffusion method was used to investigate the resistance pattern of the clinical isolates against selected antibiotics. Minimum inhibitory concentration (MIC) was determined by the broth dilution method. Plate-based assays were used for the detection of efflux pumps. It was observed that 95% of the test isolates were resistant to azithromycin and 100% were resistant to clindamycin. MIC values of azithromycin ranged between 32 and 128 μg mL-1. Although 90% of isolates contained efflux pump, none of the isolates was found to have the mef(A) gene, indicating that some other efflux pump(s) might be present. Macrolide resistance gene, erm(B), was present in 25 isolates (62.5%). Other resistance genes were absent. Plasmids were absent, but class 1 integrons were present in 80% of the isolates. The occurrence of macrolide resistance in clinical Salmonella enterica serovars Typhi and Paratyphi is of particular significance in Bangladesh where azithromycin is a commonly used drug against most diseases.

A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate

N-methyl-D-aspartate (NMDA) receptors (NMDAR) are classified as ionotropic glutamate receptors and have critical roles in learning and memory. NMDAR malfunction, expressed as either over- or under-activity caused by mutations, altered expression, trafficking, or localization, can contribute to numerous diseases, especially in the central nervous system. Therefore, understanding the receptor's biology as well as facilitating the discovery of compounds and small molecules is crucial in ongoing efforts to combat neurological diseases. Current approaches to studying the receptor have limitations including low throughput, high cost, and the inability to study its functional abilities due to the necessary presence of channel blockers to prevent NMDAR-mediated excitotoxicity. Additionally, the existing assay systems are sensitive to stimulation by glutamate only and lack sensitivity to stimulation by glycine, the other co-ligand of the NMDAR. Here, we present the first plate-based assay with high-throughput power to study an NMDA receptor with sensitivity to both co-ligands, glutamate and D-serine/glycine. This approach allows the study of different NMDAR subunit compositions and allows functional studies of the receptor in glycine- and/or glutamate-sensitive modes. Additionally, the method does not require the presence of inhibitors during measurements. The effects of positive and negative allosteric modulators can be detected with this assay and the known pharmacology of NMDAR has been replicated in our system. This technique overcomes the limitations of existing methods and is cost-effective. We believe that this novel technique will accelerate the discovery of therapies for NMDAR-mediated pathologies.

A High-throughput Calcium-flux Assay to Study NMDA-receptors with Sensitivity to Glycine/D-serine and Glutamate.

N-methyl-D-aspartate (NMDA) receptors (NMDAR) are classified as ionotropic glutamate receptors and have critical roles in learning and memory. NMDAR malfunction, expressed as either over- or under-activity caused by mutations, altered expression, trafficking, or localization, can contribute to numerous diseases, especially in the central nervous system. Therefore, understanding the receptor's biology as well as facilitating the discovery of compounds and small molecules is crucial in ongoing efforts to combat neurological diseases. Current approaches to studying the receptor have limitations including low throughput, high cost, and the inability to study its functional abilities due to the necessary presence of channel blockers to prevent NMDAR-mediated excitotoxicity. Additionally, the existing assay systems are sensitive to stimulation by glutamate only and lack sensitivity to stimulation by glycine, the other co-ligand of the NMDAR. Here, we present the first plate-based assay with high-throughput power to study an NMDA receptor with sensitivity to both co-ligands, glutamate and D-serine/glycine. This approach allows the study of different NMDAR subunit compositions and allows functional studies of the receptor in glycine- and/or glutamate-sensitive modes. Additionally, the method does not require the presence of inhibitors during measurements. The effects of positive and negative allosteric modulators can be detected with this assay and the known pharmacology of NMDAR has been replicated in our system. This technique overcomes the limitations of existing methods and is cost-effective. We believe that this novel technique will accelerate the discovery of therapies for NMDAR-mediated pathologies.

Abstract 1340: Assessing autophagic flux in cell culture models with a novel plate-based assay

Abstract The importance of autophagy in normal cell health and diseased states, including cancer, immunology and inflammation, has become quite clear. Given the growing interest in screening for autophagy modulators, we have developed a homogeneous plate-based assay to measure autophagic flux in cell culture models using NanoLuc® Binary Technology (NanoBiT™). LC3B (Atg8) protein was tagged on its N-terminus with an 11 amino acid peptide, (HiBiT), as well as an intervening “spacer” sequence. When expressed at low-to-moderate levels in mammalian cell lines, this LC3-based reporter is subject to degradation by the autophagic pathway. Changes in reporter levels following cell treatment are determined by addition of a lytic reagent containing Large BiT (LgBiT), which rapidly associates with HiBiT to produce a bright, luciferase activity in the presence of added substrate. In stable U2OS reporter cells, mTORC inhibitor treatment decreased assay signal by 25% (rapamycin) to 60% (PP242, AZD8055), consistent with compound stimulation of autophagic flux and degradation of the autophagy reporter. In contrast, treatment with autophagy inhibitors (bafilomycin A1, chloroquine) produced a 70-80% increase in assay signal, consistent with accumulation of autophagy reporter following blockade of basal autophagy. Similar results were obtained in HEK293 cells stably expressing the reporter, as well as in cells in which autophagy reporter was transiently expressed via simple, one-step transduction with BacMam viral particles. Mechanism of action of autophagy modulators was confirmed through blockade of effects by 50nM bafilomycin A1 cotreatment. Multiplex with a cell necrosis detection agent allowed for same-well determination of cytotoxic effects that might undermine analysis of a compound's discrete effects on autophagic flux. When assayed in 384-well plates with automation, U2OS and HEK293 autophagy reporter cells produced Z' values of 0.6-0.7 in response to autophagy induction (PP242), and Z' values of 0.7-0.8 by subsequent blockade of autophagy (PP242 + bafilomycin A1). Therefore, using this novel plate-based assay system for the determination of autophagic flux, it is possible to screen test agents and quantitatively assess their effects in cell culture models. Citation Format: Dan F. Lazar, Ryan W. Kessens, Amani A. Gillette, Braeden L. Butler, Christopher T. Eggers, Brock F. Binkowski, Gediminas Vidugiris, Michael R. Slater, Dongping Ma, James J. Cali. Assessing autophagic flux in cell culture models with a novel plate-based assay [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1340.